Method for adding solid metal to molten metal

ABSTRACT

THE DISCLOSURE TEACHES A METHOD FOR ADDING SOLID METAL TO MOLTEN METAL, ESPECIALLY WITHOUT DELETERIOUS REACTION WITH AIR. THE METHOD IS CHARACTERIZED BY PROVIDING THE SOLID METAL IN ROD OR WIRE FROM CLAD WITH A MATERIAL COMPATIBLE WITTH THE MOLTEN METAL AND FEEDING THE CLAD MATERIAL INTO THE MOLTEN METAL. THE DISCLOSURE TEACHES NOVEL COMPOSITES TO ACHIEVE THIS END. THE METHOD IS PARTICULARLYY USEFUL IN DEOXIDIZING MOLTEN METAL.

United States Patent 3,738,827 METHOD FOR ADDING SOLID METAL T MOLTEN METAL Michael J. Pryor, Woodbridge, Jacob Crane, Hamden, and Joseph Winter, New Haven, Conn., assignors to Olin Corporation No Drawing. Filed July 29, 1970, Ser. No. 59,348

Int. Cl. C2211 15/14, 9/10 US. C]. 75-76 7 Claims ABSTRACT OF THE DISCLOSURE The disclosure teaches a method for adding solid metal to molten metal, especially without deleterious reaction with air. The method is characterized by providing the solid metal in rod. or wire form clad with a material compatible with the molten metal and feeding the clad material into the molten metal. The disclosure teaches novel composites to achieve this end. The method is particularly useful in deoxidizing molten metal.

BACKGROUND OF THE INVENTION The present invention relates to a novel means for adding solid metal to molten metal, preferably continuously, particularly the art of deoxidizing molten metal.

Many metals present practical difficulties when they are added to a molten metal mass. It will be readily appreciated, however, that it is necessary to add these materials to the molten metal by the most convenient way possible. I

Metals of the lanthanide series are added to molten metal for a variety of reasons. These additions are commonly added to the melt in bulk form prior to the initiation of casting. They are known to improve the properties of lead bronzes and tin-lead bronzes. They are known to prevent burn-out in aluminum-magnesium alloys. They are also known to be highly useful in deoxidizing copper and copper base alloys.

For example, commercial unalloyed copper is usually marketed as electrolytic tough pitch copper (ETP) which generally has a retained oxygen level in the cast product of between 0.02 and 0.06% oxygen. The properties of ETP copper are similar to commercial oxygen-free, high conductivity (OFHC) copper, with the exception that ETP copper does not resist hydrogen embrittlement, and in certain severe forming operations, does not perform as well as oxygen-free, high conductivity copper. These disadvantages are attributable to the presence of cuprous oxide in ETP copper. Several elemental alloying additions are commonly added to control this problem, including the use of phosphorus deoxidized and boron deoxidized copper. Another way of controlling the problem is through the use of careful, controlled, artificial atmospheres and handling, as in the case of oxygen-free, high conductivity copper.

Metals of the lanthanide series are effective in reducing copper oxide and, therefore, providing an improved deoxidized copper which overcomes the foregoing dis advantages attributed to the performance of ETP copper. However, the addition of one or more solid metallic elements of the lanthanide series to a molten copper mass added to the melt prior to casting presents particular difficulties arising from the reactivity of these elements with air. The problem manifests itself in the formation of large clinker type oxides which can plug molten metal flow channels and appear as gross segregated impurities in the final ingot. This problem has been circumvented by melting in vacuum or inert gas atmospheres. However, melting in controlled atmospheres is a poorer solution for 3,738,827 Patented June 12, 1973 commercial preparation because it results in increased manufacturing costs.

In addition to the illustration given above, frequently the addition of solid materials to a particular molten mass presents problems which require the utilization of commercially awkward and expensive devices in order to prevent these undesirable and deleterious side reactions and/ or maintain adequate control of the desired amount of addition.

Other elements, such as boron, zirconium, titanium, chromium, magnesium and vanadium may be added for strengthening and other benefits. These may also cause severe problems when added directly to the melt and require special, often expensive, precautions in order to insure retention of the addition in useful form. The addition of boron and zirconium to copper, for example, causes problems in maintaining control for these additions, especially at the low level at which they are normally added. The problem with adding such elements relates both to avoiding oxidation and reaction with certain melt covers because of an undesirable reaction product and also because of distribution and control of level of addition. Similar problems exist in air melted or reactive environments, including reactions with atmospheres, containers (crucible materials), or melt covers, such as fluxes. Problems also exist with respect to additions of many other elements used in small amounts for grain size control in non-ferrous alloys, such as aluminum and nickel, and for stabilizing purposes as in stainless steels. For example, titanium boride as a grain refiner in aluminum and columbium and titanium additions to stainless steel and boron in nickel.

Accordingly, it is a principal object of the present invention to provide a method for adding a solid metal to a molten metal mass.

It is a further object of the present invention to provide a method as aforesaid which is readily practiced on a commercial scale.

It is a still further object of the present invention to provide such a method which avoids deleterious reactions, such as deleterious reactions with air.

It is an additional object of the present invention to provide novel composites.

Further objects and advantages of the present invention will appear from the ensuing discussion.

SUMMARY OF THE INVENTION In accordance with the process of the present invention the foregoing objects and advantages are readily achieved.

The present invention provides a method for adding a. solid metal to a molten metal 'mass, especially without deleterious reactions with air. The process comprises:

(A) providing a molten mass of metal;

(B) providing a solid metal, preferably in rod or wire Naturally, when the solid metal is not in rod or wire form, said solid metal must be substantially covered by the cladding.

The present invention is particularly useful in deoxidizing metal and especially deoxidizing copper base alloys with a metal of the lanthanide series in view of the difiiculties known heretofore in this art.

Accordingly, the present invention also provides a novel composite rod or wire which comprises a metal of the lanthanide series clad with a dissimilar metal, preferably clad with copper or a copper base alloy.

It should be recognized that the present invention is admirably suited for use in any method wherein it is necessary or desirable to add a solid metal to a molten metal mass, especially where it is necessary to exercise particular precautions to avoid deleterious reactions with air. For example, in many cases it is mandatory that certain covers or fluxes be used to protect the molten base metal alloy or to provide some desired reaction with the molten bath. Often such materials are incompatible with certain additions. For example, the use of carbon covers although compatible with copper is incompatible with many desirable alloy additions, such as zirconium, titanium and chromium, which all combine with carbon to form undesirable carbides. Often, this provides difiiculties in getting the addition into solution without removing the cover and, therefore, resulting in undesirable exposure of the melt to air. Cladding of the addition prevents this premature side reaction.

Other examples can readily be cited for other nonferrous metals as well as ferrous alloys. In these cases, general practice has been to add the diflicult addition by means of a master alloy. Requirements for the master alloy frequently cause an expensive product which can usually be accommodated commercially only when the addition is quite small. Aside from these economic factors, many master alloys do not circumvent homogeneity and solutionizing problems.

The present invention circumvents many of these undesirable conditions. It allows, in particular, the addition to be made in a controlled fashion at the point of the melting or casting operation that is most desirable from the standpoint of the addition. Further, the present invention also prevents the interaction problems cited above.

DBTAllED DESCRIPTION The method of the present invention is particularly suitable in deoxidizing copper or copper base alloys with a metal of the lanthanide series. Accordingly, the present invention will be discused with particular reference to this art. It should be understood, however, that the present invention is more broadly relevant, as stated hereinabove.

By using the method of the present invention, it has been found that the problem of reactions of rare earth metals with air is circumvented without the expense of melting in a vacuum induction furnace. In accordance with the present invention it has been found ETP copper may be readily deoxidized using a metal of the lanthanide series and that this can be achieved commercially using air melting.

In accordance with the method of the present invention any copper base alloy may be conveniently utilized as the molten mass of metal. As stated hereinabove, the present invention readily provides a simple and convenient method for deoxidizing these copper base alloys.

A key feature of the present invention is the provision of a composite rod or wire which comprises a metal of the lanthanide series clad with a dissimilar metal. The dissimilar metal should be compatible with the molten mass of metal to which the composite is added.

The clad rod or wire can be provided in various lengths and at various diameters.

The relationship of cladding to core dimensions can be chosen on the basis of the required addition. It is a principal intention of the present invention to provide a means for readily and conveniently incorporating alloying additions into the melt, generally in minor amounts up to 10% Therefore, the rod diameter must be proportionately related to casting rate. In an example, ETP copper was deoxidized with misch metal clad copper rod according to the present invention. When casting at a rate of 800 lbs. per minute, 0.450" rod (misch metal clad with 0.030" copper) was fed at a rate of 25" per minute. This was sufiicient to give at 0.10% alloying addition to the melt.

Thus, in the preferred embodiment, the clad rod will vary from 0.125 to 1.0 inch in diameter, with the cladding preferably comprising from 5 to 25% thereof.

If the metal of the lanthanide series is introduced unclad, unusual precautions are necessary. Accordingly, the present invention enables the introduction of the deoxidizing metal without the necessity of taking these unusual precautions.

It is preferred that the cladding be copper since it does not contain any impurities at levels that will elfect the product deleteriously. Furthermore, since its melting temperature is significantly higher than that of the lanthanide, the lanthanide will be protected until it is submerged beneath the level of the molten stream of copper. This reduces the lanthanide losses but more importantly prevents the formation of gross lanthanide oxide-coppercarbon clinkers which form the slag subsequent to deoxidation of copper when the lanthanide is added to a melting furnace of copper.

Any metal of the lanthanide series may be utilized, such as cerium or lanthanum or misch metal. Misch metal is a mixture of rare earth metals containing a major amount of cerium, a minor amount of lanthanum and various other rare earth metals in smaller amounts. The preferred material is misch metal or cerium.

Since these materials are pyrophoric when reasonably pure, the use of bare lanthanide metal rods is hazardous in the presence of heat, such as that from the molten copper stream. Cladding in the manner of the present invention prevents such a hazard because only the lanthanide metal at the tip of the clad rod is exposed and this would normally be submerged in the melt.

The clad material may be readily prepared commercially. For example, misch metal may be inserted in commercial copper tubing and the assembly drawn through a drawing die which readily clads the misch metal to the copper tubing. Naturally, other methods may be utilized, if desired.

The control of the misch metal addition to the melt is maintained by selection of rod or wire diameter and rate of feeding into the melt.

As stated hereinabove, the present invention is highly advantageous in other systems, several of which have been referred to hereinabove. Thus, for example, steel clad misch metal for boiler plates may be fed into the poor stream. Copper covered magnesium or magnesium alloys are highly useful for adding magnesium to copper alloys. Similarly, one may readily use copper clad zirconium, titanium, or copper clad copper base alloys containing zirconium, phosphorus and so forth.

In general, the cladding should be the base metal itself or a metal compatible therewith and the core either the elemental addition or a master alloy thereof. Several other systems include adding magnesium, manganese, boron and/ or titanium into copper, nickel or ferrous alloys. Also, for example, lithium, gallium, sodium and/or calcium may be readily added to nickel and copper systems in accordance with the present invention as a means of broadening alloying availability.

The present invention will be more readily understandable from a consideration of the following illustrative examples.

EXAMPLE I An 8000 pound charge of ETP copper was induction melted using a charcoal-graphite cover in a commercial sized melting furnace. The residual oxide level was brought down to below 0.02% as determined by metallographic analysis. An 0.15% charge representing 12 pounds of misch metal Was introduced and stirred both mechanically and electrically through the use of the inductive motor action to provide homogeneity. Of the 8000 pound charge, 6000 pounds were cast into a 5 /2" thick x 28 /2" wide rolling ingot. A glassy slag was found to be entrained in the solid material which, upon subsequent analysis, was revealed to be a complex formation consisting of graphite, misch metal, copper and other impurities. The material was not useable.

EXAMPLE II A clean furnace was charged with an 8000 pound charge of ETP copper and deoxidized with a charcoalgraphite cover to the 0.02% oxygen level in a manner similar to Example I. Instead of charging the misch metal to the furnace and stirring to achieve homogeneity. 4 diameter misch metal rods which had been encased (clad) in a copper tube were continuously fed into the stream of molten copper as it entered the 5% x 28 /2" mold. An amount equivalent to 0.10% which was equal to 8 pounds was carefully and uniformly introduced. The resulting ingot had discrete fine particles of misch metal oxide, but no gross glass-like slag inclusions were obvious as in Example I. The material was useable.

EXAMPLE III An experiment was conducted to determine whether bare misch metal could be used instead of the copper clad product. A section of A" extruded rod, 2-feet long was clamped in a vise and torch heated at the opposite end to bring the misch metal to its melting point of 1600 F. Long before approaching this elevated temperature, the misch metal ignited and was consumed in a violent combustion reaction.

This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein.

What is claimed is:

1. A method for deoxidizing a molten metal mass selected from the group consisting of copper and copper base alloys which comprises:

(A) providing a molten mass of metal to be deoxidized selected from the group consisting of copper and copper base alloys;

(B) providing a deoxidizing solid metal of the lanthanide series in rod or wire form clad with a material compatible with said molten mass, said material substantially covering the lanthanide, wherein the diameter of the cladmaterial is from 0.125 inch to 1.0 inch, with the cladding comprising 5 to 25% thereof; and

(C) simultaneously adding said lanthanide to the molten mass, deoxidizing said molten mass without deleterious reaction with air and adding said cladding to the molten mass by feeding said clad material in air into said molten mass.

2. A method according to claim 1 wherein an excess 1 3. A method according to claim 1 wherein said metal of the lanthanide series is misch metal and wherein said cladding is copper.

4. A method according to claim 1 wherein said clad material is continuously fed into the molten mass.

5. A method according to claim 1 wherein said clad material is continuously fed into a stream of said molten mass.

6. A method for deoxidizing a molten metal mass selected from the group consisting of copper and copper base alloys which comprises:

(A) providing a molten mass of metal to be deoxidized selected from the group consisting of copper and copper base alloys;

(B) providing a deoxidizing, solid metal of the lanthanide series in rod or wire form clad with copper, said copper substantially covering the lanthanide, wherein the diameter of said clad material is from 0.125" to 1.0", with the cladding comprising 5 to 25% thereof; and

(C) simultaneously adding said lanthanide to the molten mass, deoxidizing said molten mass without deleterious reaction with air and adding said copper to the molten mass by continuously feeding said clad material in air into a stream of said molten mass.

7. A method according to claim 6 wherein said molten mass is ETP copper and wherein the resultant product is deoxidized copper.

References Cited UNITED STATES PATENTS 1,869,498 8/1932 Osborg -76 2,085,802 7/1937 Hardy 7558 2,595,292 5/1952 Reece 75122 2,705,196 3/1955 Wever 7558 2,997,386 8/ 1961 Feiehtinger 75--129 X 3,056,190 10/1962 Chisholm 75-130 A X 3,065,070 11/1962 Otani 75-130 3,356,489 12/1967 Feichtinger 75-129 X 3,459,537 8/1969 Hornak 75-l29 X 3,634,075 1/1972 Hoff 75135 3,525,605 8/ 1970 Pyana et al. 75-76 OTHER REFERENCES Clifford A. Hampel: Rare Metals Handbook, Reinhold Publishing Corp., New York, 1954, pp. 343 and 344.

L. DEWAYNE RUTLEDGE, Primary Examiner I. E. LEGRU, Assistant Examiner US. Cl. X.R. 

